Scorching US West heatwave ‘virtually impossible’ without climate change, scientists say

Scientists say the record-breaking heatwave sweeping across the western United States this week would have been “virtually impossible” without human-driven climate change.

Millions of people from the Pacific coast to the Rocky Mountains have faced unseasonably high and potentially dangerous temperatures, reaching up to 30°F (17°C) above seasonal averages.

A rapid analysis by World Weather Attribution found that climate change has made such extreme heat events four times more likely over the past decade.

Researchers note that the temperatures recorded are highly unusual for March. Even as recently as 2016, a similar heatwave would have been around 1.4°F (0.8°C) cooler.

The study examined data from 18–22 March, using weather observations and climate models to assess how global warming has influenced the intensity and likelihood of the event.

Driven by a high-pressure system, the heatwave has already broken temperature records in around 140 cities from California to Missouri. Extreme heat warnings have been issued in several states, including California, Nevada and Arizona.

Temperatures are expected to continue rising in the coming days, with the heat spreading toward the plains and southern regions. By the end of the week, up to 100 cities could break March temperature records.

Officials warn that heat is the deadliest form of extreme weather in the US, with increased risks of heat-related illnesses, particularly among vulnerable groups.

The heatwave has also impacted local economies, forcing ski resorts in California and the Tahoe region to close early or reduce operations due to rapid snowmelt.

Experts say the event highlights how climate change is disrupting long-established seasonal patterns, increasing risks for communities and ecosystems alike.